Association of Improvement in Pain With Therapeutic Response as Determined by Individual Improvement Criteria in Patients With Rheumatoid Arthritis

OBJECTIVE: To use statistical methods to establish a threshold for individual response in patient‐reported outcomes (PROs) in patients with rheumatoid arthritis. METHODS: We used an analysis of variance model in patients on stable therapy (discovery cohort) to establish critical differences (d(crit)) for the minimum change associated with a significant individual patient response (beyond normal variation) in the PRO measures of pain (0–10), fatigue (0–10), and function (Funktionsfragebogen Hannover questionnaire; 0–100). We then evaluated PRO responses in patients initiating adalimumab in a noninterventional study (treatment cohort). RESULTS: In the discovery cohort (n = 700), PROs showed excellent long‐term retest reliability. The minimum change that exceeded random fluctuation was conservatively determined to be 3 points for pain, 4 points for fatigue, and 16 points for function. In the treatment cohort (n = 2,788), 1,483 patients (53.2%) achieved a significant individual therapeutic response as assessed by Disease Activity Score in 28 joints (DAS28)–d(crit) (≥1.8 points) after 12 months of adalimumab treatment; 68.5% of patients with a DAS28‐d(crit) response achieved a significant improvement in pain, whereas approximately 40% achieved significant improvements in fatigue or function. Significant improvements in all 3 PROs occurred in 22.7% of patients; 22.8% did not have any significant PRO responses. In contrast, significant improvements in all 3 PROs occurred in only 4.4% of 1,305 patients who did not achieve a DAS28‐d(crit) response at month 12, and 59.1% did not achieve any significant PRO responses. CONCLUSION: The establishment of critical differences in PROs distinguishes true responses from random variation and provides insights into appropriate patient management.